Aspirin’s Role in Preventing Preeclampsia

In high-risk women, a regimen of aspirin cannot prevent preeclampsia but may reduce the incidence of the condition, reported researchers in Finland who studied the role of aspirin in the prevention of preeclampsia in high-risk women.¹

The results of previous studies evaluating the effect of aspirin on preeclampsia have been contradictory. Early smaller studies and some more recent meta-analyses have shown that aspirin has beneficial effects in the prevention of preeclampsia.² However, several larger studies have failed to confirm any invaluable clinical benefits of aspirin use.^2,3 Some have argued that grouping low-risk patients with high-risk patients may have masked any benefit of aspirin. Yet when high-risk patients were analyzed separately, no significant differences between patients who did or did not receive aspirin were found.

In this current study, researchers in Finland identified 152 women who had risk factors for preeclampsia as well as abnormal findings on uterine artery Doppler velocimetry.¹ Participants were then randomized to either aspirin, 100 mg/d, or placebo between 12 and 13 weeks’ gestation, and data on preeclampsia, gestational hypertension, and birthweight were compared between study groups. Data from 121 women were included in the final analysis, which showed that low-dose aspirin had no significant effect on the reduction of rates of preeclampsia, gestational hypertension, early-onset preeclampsia, or severe preeclampsia.¹

Because of the limited power of the small sample size, the study authors also conducted a meta-analysis. Included were data from their original study in addition to data from 346 women with abnormal findings on uterine artery Doppler flow velocimetry who began taking aspirin, 50 to 150 mg/d, at or before 16 weeks’ gestation. In contrast to their original findings, the meta-analysis suggested that the risk of preeclampsia and severe preeclampsia could be reduced with low-dose aspirin started before 16 weeks’ gestation.

Evidence shows that aspirin doses greater than 75 mg/d are more effective than lower doses.^4,5 Also, aspirin treatment begun before 20 weeks’ gestation is more beneficial than treatment begun after 20 weeks of gestation, although aspirin treatment initiated as early as possible is arguably more beneficial that later initiation. Based on the available evidence, aspirin use may be justified in very high-risk women, such as those who have a history of preeclampsia or hypertension. As with any medication, the decision to recommend aspirin use to reduce the risk of preeclampsia must be based on a balance of risks and benefits. Aspirin use during pregnancy is generally considered safe, however.

Pertinent Points:
- Aspirin does not prevent preeclampsia in high-risk women.
- The use of aspirin during pregnancy may, however, reduce the incidence of preeclampsia.

References:

1. Villa P, Kajantie E, Raikkonen K, et al. Aspirin in the prevention of pre-eclampsia in high-risk women: a randomised placebo-controlled PREDO Trial and a meta-analysis of randomised trials. BJOG. 2013;120:64-74.
2. Duley L. Aspirin for preventing and treating pre-eclampsia. BMJ. 1999;318:751-752.
3. Rotchell YE, Cruickshank JK, Gay MP, et al. Barbados Low Dose Aspirin Study in Pregnancy (BLASP): a randomised trial for the prevention of pre-eclampsia and its complications. Br J Obstet Gynaecol. 1998;105:286-292.
4. Duley L, Henderson-Smart DJ, Meher S, King JF. Antiplatelet agents for preventing pre-eclampsia and its complications. Cochrane Database System Rev. 2007;2. Art no: CD004659. DOI: 10.1002/14651858.CD004659.pub2.
5. Askie LM, Duley L, Henderson-Smart D, Stewart LA, for the PARIS Collaborative group. Antiplatelet agents for prevention of pre-eclampsia: a meta-analysis of individual patient data. Lancet. 2007;369:1791-1798.